Preparation And Luminescence Properties Of CaWO₄: Eu³⁺ Red Emitting Phosphor For White LED

A series of Ca1–xWO4:xEu3+(x=0.10,0.15,0.20,0.25and0.30) and Ca0.5WO4:Eu3+0.25, M+0.25(M=Li, Na and K) red phosphor samples were synthesized for whiteLEDs via a high temperature solid state reaction. The crystal structure of the sampleswas characterized by X-ray diffraction (XRD), and the effect of Eu3+and M+dopingquantity on the luminescence properties of phosphors was investigated by Fluorescencespectrophotometry. The results show that Ca1–xWO4:xEu3+and Ca0.5WO4: Eu3+0.25, M+0.25crystallines synthesized are a tetragonal scheelite structure. The phosphors can beeffectively excited by near-UV (393nm) and blue light (464nm), and the major peak islocated at615nm due to the5D0â†'7F2transition of Eu3+. Also, the optimum dopingquantity of Eu3+in Ca1–xWO4:xEu3+phosphors is25%in mole fraction, and theintroduction of alkalis ion M+as a charge compensator can improve the luminousintensity of Ca0.5WO4: Eu3+0.25, M+0.25.The optimal doping ion in phosphor is Li+.On the basis of the above research, effect on the emission property of Ca0.5WO4:Eu3+0.25Li+0.25phosphor by doping Sr2+was studied. The Sr2+doped Ca0.5WO4: Eu3+0.25Li+0.25had not changed its phase structure. But increased Ca0.5WO4: Eu3+0.25Li+0.25emission peak intensity. This was mainly due to small amount of Sr2+brought aboutlattice distortion, which resulted in the increase of luminous intensity. The experimentalresult showed that the optimal doping content of Sr2+was15%in mole fraction.Meanwhile, effect on the emission property of Ca0.5WO4: Eu3+0.25Li+0.25phosphorby doping Sm3+was studied. The result show that the series phosphors can stronglyabsorb energy in the range of near UV and emit red light at615nm. The results showthat appropriation of Sm3+effectively improve the luminous effect and the appropriatedoping concentration is15%in mole fraction.At finally, sintering temperature of effect on the emission property of Ca0.75WO4:Eu3+0.25phosphor by sol-gel method was studied. The results showed that theappropriate sintering temperature could effectively improve the luminous effect.